Treating Feline Hyperthyroidism with Methimazole (Tapazole)

Feline hyperthyroidism is one of the most common endocrine problems in cats. Cat hyperthyroidism typically occurs in older cats and can result in a change in their behavior, appetite and water intake. When a cat is diagnosed with hypothyroidism, a veterinarian may prescribe Methimazole (Tapazole) to help regulate the thyroid function.

The Feline Thyroid Explained

The thyroid gland is part of a cat's endocrine system and is located in a cat's neck. This gland has two lobes; one on either side of a cat's windpipe. The thyroid helps regulate a cat's metabolism with the production of T4 and T3 hormones. When the T4 hormone is produced, a cat's tissues absorbs it and converts it into the T3 hormone, which regulates how fast certain cells work in a cat's body.

A cat hyperthyroid condition occurs when there is an over-production of T4 and T3 hormones in the thyroid. Cat hyperthyroidism is usually an indication that a cat has thyroid cancer.

Cat hypothyroidism is the opposite of hyperthyroidism. The cat thyroid does not produce enough T3 and T4 hormones in this situation, causing a feline to have a lower metabolism. Cat hypothyroid conditions are rarely seen in cats.

Symptoms of Feline Hyperthyroidism

A cat with a hyperactive thyroid will experience weight loss. Ironically, the cat will also have a big appetite and eat a lot more. A cat with this condition will also drink a lot more water and urinate more often. Hyperthyroidism will make a cat seem more active because his heart rate has increased. Cats with hyperthyroidism may also experience gastrointestinal problems like diarrhea and vomiting. His muscles may also begin to shrink.

Hyperthyroidism in cats can be treated with medicine, surgical removal of the thyroid gland, or radioactive iodine.

Treating Feline Hyperthyroidism with Methimazole (Tapazole)

Methimazole (Tapazole) is anti-thyroid drug veterinarians prescribe most often for cats with hyperthyroidism. The advantage of a cat taking Methimazole is that it is a non-invasive therapy that is low cost. It could take several weeks for the medication to have therapeutic effects and noticeable results.

The disadvantages of a cat taking Methimazole is that the medicine will not reduce the size of the thyroid tumor, the cat will have to take medicine every day (up to three times a day) for the rest of his life, and the medication has side effects.

Side Effects of Methimazole in Cats

Side effects of Methimazole include a loss of appetite, vomiting, anemia, fever and even depression. These symptoms are usually temporary and will go away after a few months of treatment.

Low blood cell counts have also been reported in cats taking Methimazole. Other more serious side effects include damage to the liver and bone marrow, but these are rare. Occasionally, a cat will develop hypothyroidism while on this medication, which could result in hypercalcemia or having to take a thyroid supplement daily.

Cat hyperthyroidism is a serious condition that can lead to other more serious diseases if it is not treated. The prognosis for a cat with a thyroid condition is positive as treatment of this condition is typically successful.